The refrigeration industry has been working for the past few decades to find replacement refrigerants for the ozone depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) being phased out as a result of the Montreal Protocol. The solution for most refrigerant producers has been the commercialization of hydrofluorocarbon (HFC) refrigerants.
Hydrofluorocarbon refrigerants are generally used with synthetic lubricants, such as polyol esters (POE's), polyalkylene glycols (PAG's) and polyoxypropylene glycols due to poor miscibility with hydrocarbon-based lubricants, such as mineral oil (MO). Sometimes a mixture of synthetic lubricants and hydrocarbon lubricants may be used.
Historically, retrofits of systems using hydrofluorocarbon refrigerants and a mixture of POE and mineral oil required multiple oil flushes with POE to remove residual mineral oil. This procedure had the benefit of cleaning the system because dissolved contaminants were removed with POE during flushing. Partial POE retrofit procedures entail removing a significant portion of the mineral oil and replacing it with POE without performing any flushes. This partial POE retrofit procedure introduces significant amounts of POE into the system (30%-90%) without any flushing or POE removal. Contaminants dissolved by the solvency power of oil mixtures with high levels of POE can redeposit and cause system pluggage and other detrimental effects.
Therefore, there exists a need to reduce the amount of POE used to lubricate hydrofluorocarbon refrigerant compositions.